Acute hepatitis B virus (HBV) infection is generally self-limited. However, patients who remain chronically infected are at increased risk for chronic hepatitis, cirrhosis and liver carcinoma. Only a minority of these patients can be cured by antiviral therapy. Establishing strong immune responses to HBV with a vaccine alone, or in the context of the low viral loads achievable with current antiviral drug therapy, could help induce remission or even cure the disease. Based on the ability to induce strong cellular immune responses, plasmid DNA (pDNA) vaccines are a promising modality for chronic hepatitis B. However, successful development of pDNA immunization for this indication has been hampered by the low magnitude and inconsistent responses characteristic of current pDNA delivery modalities. Using its TriGridTM electroporation (EP) DNA delivery technology, Ichor has demonstrated a dramatic increase in potency and immunogenicity of pDNA vectors encoding HBV antigens in animal models. Based on these results, it is our hypothesis that Ichor EP-based pDNA vaccination against HBV subunits can form the basis for an effective therapeutic vaccination against chronic HBV infection. In order to assess the validity of this hypothesis and demonstrate the basic feasibility of the proposed approach, we will conduct an evaluation of efficacy in an accepted disease model: Ichor has established relationships with clinicians and researchers to enable evaluation of its DNA vaccine approach in the woodchuck model of chronic viral hepatitis. Feasibility of a therapeutic HBV DNA vaccine will be assessed by characterizing immunological, virological, and safety endpoints in the woodchuck model. Additional evaluation of key safety endpoints identified by the FDA will be conducted in rabbits. The data collected in SBIR Phase I will form the basis for the submission of an IND enabling initiation of a Phase I clinical study to be conducted under SBIR Phase II. Relevance of the research to public health - Chronic infection with hepatitis B virus is associated with serious morbidity, significant health care costs, and the risk of contamination to others, which is a huge public health problem. Current antiviral therapies decrease viral loads without completely eliminating the virus. The treatment of this condition would be much improved by a safe and effective vaccine therapy that could durably eradicate the virus. [unreadable] [unreadable] [unreadable]